1,3,5-tris(4'-hydroxyphenyl)benzene falls into the class of compounds known as trisphenyls. Trisphenyls have been recognized as useful intermediates in the preparation of more complex organic structures. For example, resins are readily prepared by a reacting trisphenyls with formaldehyde, acid anhydrides and more importantly with epichlorohydrin. Epoxide resins prepared from such compounds exhibit low shrinkage, extraordinary hardness, chemical inertness, outstanding mechanical strength, and a variety of beneficial features. See, for example, U.S. Pat. No. 4,394,496; and, the above-referenced application of Hilton.
1,3,5-tris(4'-hydroxyphenyl)benzene (THPB) molecules are particularly useful in their ability to stabilize polycarbonates. This is accomplished via a three site rigid D.sub.3h crosslink. THPB molecules may also be used as crosslinking agents in epoxy resins. See, for example, Chem. Abstracts., 66, 3004C.
THPB was reported in Beilstein, E II 6, 1115 (1921). The treatment of 4-methoxyacetophenone (4-MAP) with sulfuric acid produced 1,3,5-tris(4'-methoxyphenyl)benzene (4-MAP trimer or TMPB)(20% yield). This compound was demethylated with concentrated hydrochloric acid to yield THPB.
THPB was also reported in Chimia, 12, 143 (1958) and in Chimia, 13, 105 (1959) as formed by the trimerization of 4-haloacetophenone, where the halogen is either bromine or chlorine, in the presence of potassium pyrosulfate and sulfuric acid. This reaction results in 1,3,5-tris(4'-halophenyl)benzenes. These halogen-containing trimers were treated with sodium hydroxide and converted to THPB.
M. H. Karger and Y. Mazur, J. Org, Chem, 36, 540 (1971), reported that anisole and acetyl methanesulfonate, affords 4-MAP (46% yield) and TMPB (41% yield). Subsequent to anisole acetylation, trimerization is catalyzed by methanesulfonic acid.
R. E. Lyle, E. J. DeWitt, N. M. Nichols, and W. Cleland, J. Amer. Chem. Soc., 75, 5959 (1953), report the trimerization of substituted acetophenones, i.e., 4-MAP to TMPB (54% yield), by an alcoholic hydrogen chloride solution, after four months at room temperature.
G. P. Sharnin, I. E. Moisak, E. E. Gryazin, Zhurnal Prikladnoi Khimii, 43, 1642 (1970), report the trimerization of 4-MAP to TMPB (27% yield) using a mixture of potassium pyrosulfate and sulfuric acid. See also, A. F. Odel et al., J. Amer, Chem, Soc., 36, 81 (1913).
P. Milart and J. Cioslowski, Synthesis, p. 328-29 (1984) relate to the use of 4-alkoxyacetophenones to prepare 4-alkoxyacetophenone anils which are condensed to form 1,3,5-tris(4'-alkoxyphenyl)benzenes. However, the reference does not suggest using 4-hydroxyacetophenone (4-HAP) or substituted 4-hydroxyacetophenones to produce 4-hydroxyacetophenone-anil (4-HAP-anil) or substituted 4-hydroxyacetophenone-anils, which may be then condensed to form 1,3,5-tris(4'-hydroxyphenyl)benzene or substituted 1,3,5-tris(4'-hydroxyphenyl)benzenes. In fact, the reference teaches the conversion of 4-hydroxyacetophenone to 4-alkoxyacetophenone before converting to the corresponding anil and thereafter trimerizing the anil. This is consistent with earlier teachings which describe unsuccessful efforts to trimerize hydroxyacetophenone. See, for example, G. P. Sharnin et al., supra, see also R. E. Lyle et al., supra. Its is also consistent with prior teachings that 1,3,5-tris(4'-hydroxyphenyl)benzene is produced by hydrolyzing the corresponding 4'-alkoxy substituted compound which is prepared using 4-alkoxyacetophenone. See, for example, Beilstein, E II 6, 1115 (1921). Moreover, P. Milart et al. fail to teach or suggest a one step process for trimerizing 4-HAP.
U.S. Pat. No. 3,458,473, issued Jul. 29, 1969 to Starnes et al. is directed to the preparation of various hindered trisphenyls prepared by the cyclotrimerization of an acetylphenol precursor.
U.S. Pat. No. 3,644,538 issued Feb. 22, 1972 to W. H. Starnes, discloses that both 3'-alkyl- and 3',5'-dialkyl-4'-hydroxyacetophenones can be trimerized to the corresponding triarylbenzenes with anhydrous HCl and triethyl orthoformate and ethanol. Trimerization of unsubstituted 4-HAP is not suggested or disclosed. Starnes also fails to teach or suggest trimerizing substituted or unsubstituted 4-HAP-anil.
German Patent 258,929 to Zimmerman et al., issued Aug. 10, 1988 is directed to methods for the production of 1,3,5-tris(triarylbenzene) compounds. These compounds are reacted by combining 2,4,6-triaryl pyrylium salts with carboxylic acid anhydride in the presence of a basic condensing agent. The reaction of Zimmerman utilizes triaryl pyrylium carboxylic anhydride.
Elmorsy et al., "The Direct Production of Tri- and Hexa-Substituted Benzenes from Ketones Under Mild Conditions," Tetrahedron Letters, Vol. 32, No. 33, pp. 4175-4176 (1991) report the treatment of aryl benzenes with tetrachlorosilane in ethanol to yield 1,3,5-triarylbenzenes. However, Elmorsy et al. fail to teach or suggest trimerizing 4-hydroxyacetophenone, a 4-hydroxyacetophenone derivative, or a 4-substituted-oxyacetophenone by contacting such a compound with a halosilane, as in the present invention. Indeed, it is believed that trimerizing a hydroxyacetophenone such as 4-hydroxyacetophenone or a 4-hydroxyacetophenone derivative, is not disclosed or suggested by Elmorsy et al. because of the belief that the hydroxy group would interfere with the reaction, for example, react with the tetrachlorosilane. See, e.g,, Sharin et al., supra, which illustrate why it was believed, before now, that direct trimerization of hydroxyacetophenone was not feasible. Accordingly, Elmorsy et al. fail to teach or suggest the present invention.